1. Field of the Invention
This invention relates to a protective device for a circuit interrupter and, more particularly, it pertains to an adjustable thermal trip unit for varying the thermal rating of the circuit breaker.
2. Description of the Prior Art
Circuit breakers having thermo tripping mechanisms are well known in the art and consist primarily of a movable trip bar which carries a releasable latch. As shown in U.S. Pat. No. 3,211,860, the trip bar is actuated by adjacent bimetal strips which respond to temperature generated by an overflow current flowing through the circuit breaker. A circuit breaker of that type is set for a given amperage rating which is conventional for circuit breakers used in some countries such as the United States. There is, however, a preference for manually adjustable thermal tripping devices to change the thermal rating of the circuit breaker to suit load requirements.